Authorities in the UK have given the green light for the use of the Oxford University / AstraZeneca coronavirus vaccine.
The UK medicines regulator says the vaccine has met its "strict standards of safety, quality and effectiveness".
Plans are now being put in place to roll out the new vaccine across the UK.
However, a decision on its use in Ireland and the EU is not expected for several weeks.
It follows approval for the Pfizer / BioNTech vaccine, which began to be administered in Ireland yesterday.
Unlike the Pfizer and Moderna vaccines, the Oxford one does not need to be stored at ultra-low temperatures - meaning the rollout is expected to be quicker and cheaper than the other jabs.
Trials have shown a lower efficacy rate for the Oxford vaccine - which is based on more traditional vaccine technology - compared to the mRNA-based Pfizer and Moderna jabs.
However, the Oxford vaccine is seen as a crucial factor in ensuring a widespread global vaccination programme can be scaled up in the coming months.
Ireland is expected to be in line for over 3 million doses of the Oxford vaccine if it's approved by EU regulators.
A number of reports have indicated the vaccine may not receive the green light for use in the EU in January, with officials saying they're waiting for more data.
The European Medicines Agency has also not yet received an application from AstraZeneca for conditional marketing authorisation yet, EMA Deputy Executive Director Noel Wathion told Belgian newspaper Het Nieuwsblad.
However, EU regulators could make a decision on the Moderna vaccine as early as next week.